In a field of a graphic art, in order to improve a reproduction of an image of a continuous gradation with a halftone dot image or a reproduction of a line image, an image-forming system showing a ultrahard (in particular, gamma (.gamma.) is 10 or more) photographic characteristic is required.
A lithographic developing system utilizing a so-called "infectious development effect" has been used from the past as a method for obtaining a photographic characteristic of a high contrast but it has a defect that a developing solution is instable and difficult to use.
Meanwhile, a method. for obtaining it with a more stable developing solution includes the methods described in U.S. Pat. Nos. 4,224,401, 4,168,977, 4,166,742, 4,311,781, 4,272,606, 4,221,857, 4,332,878, 4,634,661, 4,618,574, 4,269,922, 5,650,746, and 4,681,836.
The image-forming system is a system in which a silver halide photographic material of a surface latent image type containing a hydrazine derivative is processed in a stable MQ developing solution of pH 11 to 12.3 (an MQ developing solution means a developing solution using hydroquinone and p-aminophenol in combination) or a PQ developing solution (which means a developing solution using hydroquinone and 1-phenyl-3-pyrazolidones in combination) to obtain a ultrahard negative image having .gamma. exceeding 10.
According to this process, a photographic characteristic of a ultrahard contrast and a high sensitivity can be obtained and sulfite of a high concentration is allowed to add to a developing solution. Accordingly, a stability of the developing solution against air oxidation is improved with great strides as compared with a conventional lithographic developing solution.
With respect to a light-sensitive material for a daylight which is used for a dot to dot work process, trying to faithfully carry out, for example, a superposed dot to dot work of a halftone dot original and a line image original requires a ultrahard image-forming system. The image-forming system described above using a hydrazine derivative is effective as well for this purpose, and the specific examples for application thereof are disclosed in JP-A-62-640 (the term "JP-A" as used herein means an unexamined published Japanese patent application), JP-A-62-235938, JP-A-62-235939, JP-A-63-104046, JP-A-63-103235, JP-A-63-296031, JP-A-63-314541, and JP-A-64-13545.
Meanwhile, it is well known in the arts that endiols such as ascorbic acid functions as a developing agent and are paid attention as a developing agent having no ecological and toxicological problems described above. It is indicated in, for example, U.S. Patents 2,688,549 and 3,826,654 that an image formation is possible under a high alkaline condition of at least pH 12 or higher. However, an image of a high contrast can not be obtained with these image-forming processes.
Increasing a contrast with a developing system using ascorbic acid has been tried to some extent. For example, Zwicky indicates that a kind of a lithographic effect is developed when ascorbic acid is used as a sole developing agent (J. Phot. Sc. Volume 27, pp. 185 (1979)) but it was a system having a pretty low contrast as compared with a case of a hydroquinone developing agent system. Further, a system in which a di-quaternary ammonium salt and ascorbic acid are used in combination is disclosed in U.S. Patent T896,022 and JP-B-46939 (the term "JP-B" as used herein means an examined Japanese patent publication) but an effect for an increased contrast is scarcely found while a development accelerating effect is seen. An effect for a combined use of ascorbic acid and a quaternary salt is described as well in JP-A-3-249756 and 4-32838 but a contrast of an image obtained is not sufficient.
Further, it is indicated in JP-A-5-88306 that a high contrast can be obtained by using ascorbic acid as a sole developing agent and maintaining pH to 12.0 or higher but a problem is involved in a stability of the developing solution.
There also is a case (U.S. Pat. No. 3,730,727) that use of a specific developing solution using ascorbic acid and a hydrazine derivative as the main components can provide a developing system giving a high sensitivity and low stain and fog but nothing is described on an improvement in a contrast.
A ultrahard image-forming system using a hydrazine derivative is a system using a dihydroxybenzene compound such as hydroquinone as a developing agent as described above and has several disadvantages from ecological and toxicological points of view. For example, hydroquinone is an undesirable component because of an allergic disadvantages, and 1-phenyl-3-pyrazolidones are a component having an inferior biodegradation. Further, sulfite of a high concentration shows a high COD (chemical oxygen demand). In this image-forming system, amines described in U.S. Pat. No. 4,975,354 are usually used in combination but not preferred in terms of a toxicity and a volatility.
Accordingly, the object of the present invention is to provide a novel image-forming process which makes it possible to obtain a high contrast image required in a graphic art field by using a developing solution having no problem against an ecological system and a working environment.